Hydraulic pump or motor



Dec. 5, 1961 FIG.|

R. W. BRUNDAGE HYDRAULIC PUMP 0R MOTOR Filed Oct. 1, 1956 3,011,447 Patented Dec. 5, 1961 This invention pertains to the art of hydraulic pumps or motors and more particularly to a rotary, positive displacement, hydraulic pump or motor.

The invention is particularly applicable to internal gear type, rotary pumps or motors of the variable volume or variable speed type and will be described with particular reference thereto although it will be appreciated that the invention is equally applicable to, without limitation, vane or barrel-type pumps or motors of either vari- The circumferential width of these lands relative to the width of the passage heretofore has been a very important part of pump design and operation.

Thus, if the width of the land is narrower than the width of the passage, then for an instant in the arc of rotation of the passage past the land, fluid can leak around the land from the outlet manifold to the inlet manifold through the passage. With high pressure pumps, substantial amounts of fluid can leak past the land in such event. This is ordinarily called leakage.

If the land is wider than the passage and, for example, the land is positioned adjacent the point in the movement of the' chambers where they are decreasing in volume then'for an instant in the arc ofrotation no fluid can leave the chamber and very high pressures within the chamber can result. This is ordinarily termed trapping and is considered very detrimental in pumps of the" type to which this invention pertains.

In my co-pending applications, Serial No. 497,779 filed March 29, 1955, now Patent No. 2,898,862, Serial No.

548,022, filed November 21, 1955, now Patent No. 2,956,- 506, and Serial No. 573,292, filed March 22, I956, now Patent No. 2,925,044, various arrangements are proposed for either mitigating or completely alleviating the undesirable effects of either leakage or trapping.

In the course of carrying on experiments with the embodiments described in the above-referred to patent applications, additional problems began to present themselves. One of such problems was that of a lowering volumetric efliciency as the speed of rotation of the pump increased, which lowering of volumetric efficiency appeared to be due to the failure to be able to get the inflowin-g hydraulic fluid into the increasing volume chambers; in other words, the suction pressure in the increasing volume chambers was such as to cause the hydraulic fluid to vaporize, an effect normally called cavitation. The present invention in part deals specifically with this problem.

The present invention contemplates a new and improved hydraulic pump or motor of the general type described which overcomes all of the above-referred to difficulties and others and provides a hydraulic pump or motor having high volumetric and mechanical efficiency.

In accordance with the present invention, a positive displacement hydraulic pump or motor is provided comprised of a plurality of rotatable members arranged so as to define a plurality of alternately increasing and decreasing volume chambers, inlet and outlet manifolds axially aligned with the chambers arranged to be alternately communicated with the chambers and a ported disc positioned between the chambers and the manifolds and rotatable with the chambers, the disc having a plurality of generally axially extending passages, one for each chamber through which all fluids into and out ofthe chamber must flow, each passage being sloped either outwardly in the direction of flow of fluid from the inlet manifold into the chambers whereby centrifugal forces assist in moving the fluid into the increasing volume chambers or forward toward the manifolds in the direction of rotation whereby there will be a tendency to scoop the oil out of the inlet manifold and forceit into the increasing volume chambers, or both.

The principal object of the invention is the provision of a new and improved hydraulic pump or motor which overcomes all of the dificulties of the prior art and provides high mechanical and volumetric efficiency.

Another object of. the invention is the provision of a new and improved arrangement for assisting the flow of hydraulic fluid into increasing volume chambers of a hydraulic pump or motor.

The invention may take physical form in a variety of combinations of parts and sub-combinations of parts, a preferred embodiment of which will be described in detail in this specification and illustrated in the accompanying drawing which is' a part hereof and wherein:

FIGURE 1 is a side cross-sectional view of a hydraulic pump or motor constructed in accordance with the invention,the section line being taken approximately 011 the line 11 of FIGURE 5.

FIGURE 2 is a similar view but taken on the line 22 of FIGURE 5.

FIGURES 3, 4, and 5 are cross-sectional views of FIGURE 1 taken approximately on the section lines 33, 4 -4, and 55 thereof.

Referring now to the drawings wherein the showings are for the purposes of illustrating a preferred embodiment of the invention only, and not for the purpose of limiting same, the various figures show a housing 16; a drive shaft 11, inner and outer members 12, 13 respectively, defining therebetween increasing and decreasing volume chambers 14, 15 respectively; a ported disc 16 rotatable with the inner member and having a plurality of passages 17,. one

' for each chamber 14, 15 for the purpose of communicatting the chambers with inlet and outlet manifolds 18,19;

a "sealing disc 20 mounted'on the shaft 11, and a control plate or manifold 21, the adjustment of which will vary the output volume of the pump as will appear hereinafter.

The housing 10 may take 'a number of different forms but in the embodiment shown, is comprised of a central cylindrical portion 25, aloft-end plate '26 having an opening 27 through which the shaft 11 extends, and a-rightend plate 28 in which the inlet and outlet manifolds 18, 19 are formed; The members 25, 26'and 28 all have abutting surfaces in sealing engagement to define an interior cavity in which the various members of the pump are positioned. Bolts 30 and nuts 31 hold the members in assembled relationship.

The drive shaft 11 has mounted thereon in side by side relationship, a sealing disc 20, the inner member 12 and the ported disc 16, all of which rotate the shaft.

The inner and outer members 12, 13 may take a number of different forms but in the embodiment shown are respectively, externally and internally toothed gear members with the inner member having'one, or more, less teeth than the outer member rotatably supported on an 3 axis spaced from theaxis of the shaft 11 by an eccentric ring 32 mounted on the inside of the housing 10. The eccentricity of the ring 32, the shape and dimensions of the teeth are all so proportioned that one portion of each tooth is always in sliding, sealing contact with a portion of the tooth on the opposite member to define chambers sealed from each other circumferentially. Thus as the shaft 11 rotates, the inner and'outer members 12, 13 also rotate to cause the chambers 14, 15 to increase and decrease in volume. With this arrangement, the chamhers will have a point of minimum volume indicated generally by the point It and a point of maximum volume indicated by the point x both located on what may be termed a neutral axis. Assuming a clockwise direction of rotation, as viewed in FIGURE 4, the chambers just past the point n will be increasing in volume and are indicated by the reference character 14 while the chambers which have just moved past the point x are decreasing in volume and are indicated by the reference character 15. Obviously, if the direction of rotation were reversed, this situation would also be reversed.

it is to be noted that the chambers 14, 15 extend aidally and that the members 12, 13 have a substantial,

but equal, axial length relative to their diameter. The axial length of the eccentricring 32 is slightly less than that of these members.

The ported disc 16 provides a passage of controlled circumferential width for communicating the chambers 14, 15 with the inlet and outlet manifolds 18, 19. As shown, the ported disc 16 is keyed to rotate with the inner member 12 by means of a pin 34 and one passage 17 for each chamber. Preferably, the axis of each passage 17 corresponds with the root of the teeth of the inner member 12. The circumferential width of each passage 17 is preferably equal to one-half the pitch of the teeth on the inner member 12.-

The ported disc 16 is supported for rotation in a ring 36 also mounted on the inside of the housing 10 and has one surface in sealing contact with the adjacent surface of the members 12, 13 and the other in sealing contact with the manifold 21.

As the inner and outer members 12, 13 rotate and the chambers alternately increase and decrease-in volume, hydraulic fluid is respectively sucked into and discharged from such chambers through the passage 17.

To assist the flow of fluid into the increasing volume chambers, the passages 17 are sloped outwardly in a direction towards the chambers whereby centrifugal forces on the hydraulic fluid assist its movement through the passages into the increasing volume chambers.

.Furthermore, the passages are sloped in the direction of rotation away from the chamber whereby as the -passages. 17 move by the inlet manifold, a scooping action results and the inertia of the hydraulic fluid is employed to assist its being forced into the increasingvolume cham- 'bers.

-It is believed that the use of the ported disc with passages extending generally axially, or sloped outwardly, or sloped in the direction of rotation, or in combination, is new in the pump art. A considerable increase in volumetric efliciency results with the use of passages 17.

The inlet and outlet manifolds 18, 19 are formed in the manifold housing 21 and communicate with the exterior of the end plate 28 through passages 40, 41, each termimating in a suitable means such as the fitting 42 for connecting hydraulic fluid pipes to the pump.

The inlet and outlet manifolds are communicated with the passages 17 as they rotate through arcuate ports 45, 44 respectively in the control plate 21. These ports 44, 45 are spaced from the axis of rotation of the shaft 11 the same distance'as the right-hand end of the passages 17 so that as the passages 17 rotate they will communicate alternately with the ports 44, 45. The adjacent ends of the ports 44, 45 are spaced from each other by lands 47, 48 which, in effect, separate the inlet and outlet manifolds 18, 19. The land 47 is, in efiect, divided into two auxiliary lands 47a and 4-76 by a trapping port 49 which, in the embodiment shown, opens to the outer periphery of the control plate '21. In a like manner, the land 48 is divided into two auxiliary lands ida, 48b separated by a trapping port 59 communicated with the trapping port 49 through a passage 51 formed between the outer edge of the plate 21 and the housing 14 The circumferential width of the auxiliary lands 47a, 47b, 48a, 48b and the trapping ports 49, 50 is important from the standpoint of successful operation of the invention. Preferably, the circumferential width of the lands and the ports are equal to each other and to the circumferential width of the passages 17. Thus, as any one passage 17 in communication with an increasing volume chamber 14 rotates, it is first in communication with the inlet manifold 18 through the port 44. At the same time, a passage 17 in communication with a decreasing volume chamber 15 is in communication with the outlet manifold 19 through the port 45.

As the increasing volume passage 17 passes the land 47a, it is cut off from communication with the port 44 and immediately brought'into communication with the trapping port 49'. Simultaneously, the decreasing volume passage 17 moves past the auxiliary land 48a and immediately comes into communication with the trapping port 59. Thus, these two passages are in communication with each other through the passage 51 for a small fraction of the arc of rotation. Fluid from the decreasing volume chamber 15 flows into the increasing volume chamber 14, where it serves to drive the shaft 11 by acting as though it were a motor and its energy is recovered.

The respective passages 17 tllBIllTIOV past the auxiiiary lands 47b and 43b and come into communication with the other ports 45, 44, as the case may be.

The lands 47, 48 thus each have an effective width greater than the spacing between passages 17. Normally this would prevent leakage but would cause trapping. However, the trapping ports 49, 5t and the passage 51 relieve the trapping pressures but enable recovery of the energy of the fluid discharged from the decreasing volume chamber 1 opposite the lands.

In the embodiment shown, the manifold housing 21 is positioned so that the trapping ports 49, 51 are located opposite the points of minimum and maximum volume it x respectively. The pump will thus have its maximum volume output for any given speed.

So that the volume output of the pump may be varied, the manifold housing 21 is rotatable in the housing 10. Thus, the manifold housing 21 is integral with a shaft 55 aligned with the shaft 11 and rotatably supported in and extending to the right of the end member 23. A handle 56 on the end of the shaft 55 enables the manifold housing 21 to be rotated relative to the points n x.

Thus, if the manifold housing 21 is rotated in the direction of rotation, the lands 47, 48 will be shifted relative to these points and the inlet and outlet manifolds will be in communication with different sets of both increasing volume and decreasing volume chambers 14, 15. The ratio of increasing volume chambers to decreasing volume chambers in communication with any one manifold will determine the volume output of the pump.

If the trapping ports 50, 51 are moved to be equidistant from the points it x, the pump will have no output volume. Fluid from half of the decreasing volume chambers will flow through each manifold to half the increasing volume chambers and as the rate of increase is the same as the rate of decrease, there will be no net output of the pump. However, substantially all of the pressure energy in the fluid from the decreasing volume chambers will be delivered to the increasing volume chambers as though the increasing volume chambers were a motor, so there is little loss of efliciency resulting from the bypassing of the output fluids from some of the decreasing volume chambers to some of the increasing volume chambers.

The end of the chambers 14, 15 opposite from the ported disc 16 are closed by means of the. sealing disc 20 which is in the form of a sleeve mounted on the shaft 11 and having a sealing surface 6% in sealing engagement with the left-hand end of the inner and outer members 12, 13. The sealing disc 2% is supported for axial and rotational movement in the housing 10. In the embodiment shown, it is mounted in a roller bearing 62 held against axial movements relative to the sealing disc 20 by'means of a C-ring 63 mounted in a slot in the outer surface of the sealing disc 2&3. The roller bearing 62, is, in turn, slidable ina rabbet 64 in the inner surface of the central portion 2-5 of an axial length of the.

bearing 62. p p v v.

The sealing disc 2%) thus rotates with the inner member 12 but is axially movable relative thereto. While such action may be obtained in a number of different ways, in the embodiment of the invention shown, the, sealing disc 20 is preferably rigidly attached to the shaft 11 in any suitablev manner but preferably with an interference fit. Such fit may be obtained in conventional ways such as by cooling the shaft 11 and heating the sealing disc 20 until the sealing disc 26" will fit over the shaft and then allowing the two members to reach a common temperature. i

The inner member 12 is slidably mounted on the shaft 11, however, and keyed against rotation relative thereto by the key and keyway 37. The ported disc 16 is slidable axially along the shaft 11 along with the inner member 12.

The hydraulic pressures in the chambers in communication with the outlet manifoldexert an axial force on the sealing surface 6! tending to separate. the sealing disc 20 from the left-hand end of the inner and outer members 12, 13. Likewise, such pressures will tend to force a separation between the surfaces of the ported disc 16 and the control plate 21. In either case, leakage of the pump will result. To prevent this happening, means are provided for urging the sealing disc 20 towards the inner and outer members'12, 13 with'a force sufficient to resist the hydraulic forces tending to separate the disc and the two members. As the output pressure of the pump may vary and thus the force tending to separate the disc and the two members may likewise vary, it-is' preferred that the force tending to move the disc 20 toward the members 12, 13 be made proportional to the pressure in the outlet manifold. Thus, the cavity 65 to I the left of the sealing disc 20* is communicated with the outlet manifold 19 by means of a passage 66 formed in both the central portion 25 and the end plate 28. As the amount of fluid flowing through this passage is'almost negligible, the size of the passage may be made relatively small.

The outlet manifold pressure in the chambers 14, 15 will only exert a force on efiectively'one-half of the cross-sectional area of the sealing surface 60 bearing against the ends of the members 12, 13. To exactly counteract this force, preferably approximately one-half of the cross-sectional area of the sealing disc 20 on the side remote from the sealing surface 60 is exposed to the hydraulic pressure in the cavity 65.

To prevent the hydraulic pressure in the cavity 65 from contacting the entire cross-sectional area of the sealing disc 20, an auxiliary sealing disc is provided comprised of a sleeve 68 slidably supported in a counterbore 69 in the surface of the end member 26 facing the cavity 65. An O-ring 70 fits around the sleeve 68 and provides a sealing action to prevent the fluid in the cavity 65 from leaking around the outer surface of the sleeve 68. The sleeve 68 has an axially and radially extending flange 71 on its right-hand end having a surface 72 in pressure engagement with the left-hand end of the sealing disc 20. Inwardly of the flange 71, the space 75 is sealed from the cavity 65 pressures. The flange 71 has a surface 73 t5 opposite from the surface 72 of an area'equal to one-half the area of the surface 72. Hydraulic pressure in the cavity 65 exerts an axial force to the right on the surface 73 exactly equal and opposite to the hydraulic pressures to the left on the surface 72. In both casespractically friction free operation results.

A coil spring 74 positioned within the sleeve 68 biases the entire assembly to the right. The force of the spring 7 4 need only be nominal, however.

The areas of the sealing disc or surface 73 exposed to the outlet manifold pressures may be increased beyond that stated, if desired, while still being within theinvention or made less if "the pressure of the spring 74? is increased sufiiciently.

With the arrangement axial hydraulic forces are balanced and the only pressures between the sealing surfaces is due to the spring 74. A minimum or no leakage within the pump results.

One of the problems in a pump of the general type described, however, is that the force of the hydraulic fluids on the various parts of the pump are unequally distributed about the axis and axially along the axis.

Thus, in all cases, the outlet manifold will be incommunication with approximately one-half of the chambers. The hydraulic pressures in such chambers will exert a force to the left on the sealing surface 60 over one-half force on the surface of the inner member 12 which may be generally summed up by the vector 81. This force is resisted by the force indicated by the vector 83 through the center line of the bearing 62. These two vector forces 81, 83 have a bending moment on the shaft 11 proportional to the distance M between the lines of action of the two vectors.

The forces 84), 82 and the distance L are fixed distances dependent uponthe designed capacities of the pump. On the other hand, the distance M may be varied by positioning the center line of the roller bearing 62 closer to or further from, the line of action of the vector 81. The distance M is so proportioned that the bending moment of the forces 81, 83 will be equal and opposite to'the bending moment of the forces 8! 82. With such an arrangement, bending of the various parts making up the pump can be held to a minimum and the sealing surfaces will thus always remain in sealing engagement and leakage can be held to a minimum while at the same time having a minimum of friction within that certain of the surfaces would be moved into high pressure engagement which means high friction while other of the surfaces would be moved apart which would permit leakage to occur.

It is to be noted that the sealing disc 20 has a substantial radial and axial dimension and by virtue of its interference fit on the shaft 11 contributes substantially to the rigidity of the shaft 11.

It is to be noted that both the sealing disc 20 and the ported discs 16 rotate with the inner member 12. Thus, excellent sealing can be obtained here and there is no problem of friction between the members. Further, the sealing disc 20 and the ported disc 16 have a speed of rotation relative to the outer member 13, equal only to the difference in the number of teeth between the two gears and the pitch of the teeth, Thus, there is little frictional loss here.

The novel features of the sealing sleeve 68 and the sealing disc 20 just described are further described and shown, and dimensions, the

7 claimed in my co-pending' continuation-in-part application Serial No. 16,765, filed March 22, 1960.

It is to be noted that the use of the trapping ports dividing the two lands into auxiliary lands with the trapping ports intercornmunicated one with the other, is described in my co-pending application, Serial No. 573,292, filed March 22, 1956, now Patent No..2,925,044.

The present invention deals with a pump which has an axial flow of fluid from the chambers to the inlet and outlet, manifolds, and the use of the ported disc as described is only of value when so employed. Such axial discharge may readily be obtained from either vane-type, internal-rotary-gear type, or rotating cylinder-type pumps.

It is obvious that the improvements and the invention herein described may be employed in hydraulic motors of either the rotating internal gear type,-vane type or rotating cylinder type. For the purposes ofsimplicity in the claims hereinafter reference will be made either to a pump or motor, with the understanding that whenever a pump is mentioned a motor may be indicated, or whenever a motor is indicated, a pump may be indicated. Outlet manifolds on a pump become inlet manifolds on a motor. In either case, this is the manifold having the high pressures.

The invention has been described with particular reference to a preferred embodiment. Obviously, modifications and alterations difl'ering radically in appearance from the preferred embodiment described will occur to others upon a reading and understanding of this specification, and it is my intention to include all such modifications and alterations insofar as they come Within the scope of the appended claim. I

Having thus described my invention, I claim:

In a variable volume internal gear type hydraulic pump comprised of an internally toothed and an externally toothed gear member mounted for rotation on spaced axes and having teeth in sliding sealing contact to define a plurality of pumping chambers revolving in a fixed closed path of movement; said chambers gradually increasing in volume after they pass a fixed point of minimum volume on said path of movement until they reach a fixed point of maximum volume on said path of movement and then gradually decreasing in volume until they reach said fixed point of minimum volume; means in sealing engagement with one axial end of said gear member closing one axial end of said chambers; means in sealing engagement with the other axial end of said gear member and closing the opposite axial end of. said chambers, said last mentioned means in sealing engagement with one axial end of said gear members including a disc revolving with said chambers and having a plurality of generally axially extending passages therethrough, one for each chamber and each continuously in communication with one of said chambers as the chambers revolve and means defining an arcuate inlet and an arcuate outlet manifold including a pair of spaced lands sealingly separating said manifolds at the arcuate ends one from the other, said manifolds being so located that the ends of said passages remote from said chambers are first in communication with one of said manifolds and move past a land to be in communication with the other of said manifolds and then move past the other land to be in communication with the first mentioned of said manifolds, the improvement which comprises: said passages having a uniform cross sectional area throughout their longitudinal length and having a longitudinal axis sloping radially inwardly in a direction considered away from said chambers whereby centrifugal force on the fluid in said passages create a force on the fluid urging the fluid toward the chambers and said passages also sloping in the direction of rotation when considered in a direction away from said charnbers whereby said passages will tend to scoop fluid from said inlet manifold and force the fluid into said increasing volume chambers.

References in the file of this patent UNETED STATES PATENTS 838,140 Rogers Dec. 11, 1906 1,019,521 Pratt Mar. 5, 1912 1,486,835 Hill Mar. 11, 1924 1,660,464 Wilsey Feb. 28, 1928 2,453,266 Rockwell Nov. 9, 1948 2,460,310 Rathman Feb. 1, 1949 2,484,789 Hill et al Oct. 11, 1949 2,490,115 Clarke Dec. 6, 1949 2,511,878 Rathman June 20, 1950 2,565,077 Holl Aug. 21,1951 2,580,006 Densham Dec. 25, 1951 2,608,933 Ferris Sept. 2, 1952 2,650,544 Parsons Sept. 1, 1953 2,656,972 Rathman Oct. 27, 1953 2,787,963 Dolan et a1. Apr. 9, 1957 2,898,862 Brundage 'Aug. 11, 1959 FOREEGN. PATENTS 316,670 Great Britain of 193 1 

